The present invention relates generally to a steering mechanism for a vehicle and, more particularly, to a steering mechanism for use with a patient support, such as a hospital bed, a stretcher, a patient carriage, a transport table or a cart.
The present invention provides a vehicle comprising a first wheel supported for rotational movement about a first substantially horizontal axis and supported for pivoting movement about a first substantially vertical axis. The vehicle further comprises a second wheel supported in spaced relation to the first wheel, the second wheel supported for rotational movement about a second substantially horizontal axis and supported for pivoting movement about a second substantially vertical axis. A linkage assembly includes a wheel coupling configured to provide communication between the first wheel and the second wheel, wherein a driving pivoting movement of the second wheel causes the wheel coupling to transmit a passive pivoting movement to the first wheel.
An elastic device is illustratively connected to the wheel coupling, wherein the elastic device establishes a lower torque limit below which the driving pivoting movement of the second wheel is not transmitted as a passive pivoting movement by the wheel coupling to the first wheel. A release coupling is illustratively provided in communication with the wheel coupling, wherein the release coupling establishes an upper torque limit above which the driving pivoting movement of the second wheel is not transmitted as passive pivoting movement by the wheel coupling to the first wheel.
A method of moving a patient support is also disclosed, the method comprising the steps of providing a frame coupled to the patient support surface, providing a first wheel supporting the frame, and providing a second wheel supporting the frame in longitudinally spaced relation to the first wheel. The method further comprises the steps of pivoting the second wheel about a substantially vertical axis to a driving position, and selectively driving the first wheel in pivoting movement about a substantially vertical axis in response to the driving position of the second wheel relative to the passive position of the first wheel. Illustratively, the first wheel is driven in pivoting movement only when the differential between the driving position of the second wheel and the passive position of the first wheel is at least as great as a predetermined minimum value. Further illustratively, the first wheel is driven in pivoting movement only when the differential between the driving position of the second wheel and the passive position of the first wheel is no greater than a predetermined maximum value.
In a further illustrative embodiment of the patient support of the present invention, a frame defines a longitudinal axis, a patient support surface is coupled to the frame, and a first wheel is coupled to the frame and is configured to rotate about a first substantially horizontal axis and to pivot about a first substantially vertical axis. A second wheel is coupled to the frame in longitudinally spaced relation to the first wheel, the second wheel being configured to rotate about a substantially horizontal axis and to pivot about a substantially vertical axis. The patient support further includes a handle pivotally coupled to the frame, and an input coupling operably connecting the handle and the second wheel, the input coupling configured to cause pivoting movement of the second wheel about the second substantially vertical axis in response to pivoting movement of the handle.
According to a further illustrative embodiment of the patient support of the present invention, a frame defines a longitudinal axis, a patient support surface is coupled to the frame, a first wheel is coupled to the frame and is configured to rotate about a first substantially horizontal axis and is configured to pivot about a first substantially vertical axis, and a second wheel is coupled to the frame in longitudinally spaced relation to the first wheel, the second wheel being configured to rotate about a substantially horizontal axis and to pivot about a second substantially vertical axis. A first actuator is operably coupled to the first wheel to drive the first wheel in rotation about the first substantially horizontal axis, and a second actuator is operably coupled to the second wheel to drive the second wheel in rotation about the second substantially horizontal axis. A controller is configured to cause the first actuator to drive the first wheel in a first direction about the first substantially horizontal axis and to cause the second actuator to drive the second wheel in a second direction about the second substantially horizontal axis, the first direction being opposite the second direction, in response to pivoting movement of the handle during a powered rotation mode of operation. Illustratively, the controller is further configured to cause the first actuator to drive the first wheel in the first direction about the first substantially horizontal axis and to cause the second actuator to drive the second wheel in the first direction about the second substantially horizontal axis, in response to pivoting movement of the handle during a powered slide mode of operation.
The linkage assembly of the present invention allows a vehicle to move in a manner similar to that of a vehicle including a centrally mounted fifth wheel. The linkage assembly enhances the maneuverability of the vehicle by linking a first wheel and a second wheel in a manner causing both interconnected wheels to pivot simultaneously about respective vertical axes in opposite directions. The elastic member provides for torsional play within the wheel coupling thereby allowing the vehicle to be positioned as if it had independent freely pivoting wheels. Additionally, if the release coupling is automatic, then no physical activation or manual input is required by an operator.
Additional features of the present invention will become apparent to those skilled in the art upon a consideration of the following detailed description of illustrative embodiments exemplifying the best mode of carrying out the invention as presently perceived.